With hydraulic brakes such as drum brakes or disc brakes for vehicles, the braking-gap should always be kept constant by moving the piston toward the brake linings by means of a braking-gap adjuster device, said piston serving to push the brake linings, since, due to wear caused by braking, there is an increase in the braking gap between the linings (frictional pads) and a brake drum (a brake disc).
To this end, the piston is slidably inserted through an associated cylinder to define a hydraulic chamber between the piston and a portion of the cylinder facing it. Between the piston and that portion of the cylinder, there is arranged a nut and bolt adjuster combination wherein the nut threadedly engages the bolt. The adjusting bolt abuts at its clutch section against the clutch face of the facing portion, while the adjusting nut abuts against the piston through a spring. When the braking-gap exceeds a predetermined value, the adjusting bolt is threadedly moved to advance the piston, whereby the braking-gap is kept constant.
In accordance with this automatic braking-gap adjuster arrangement, however, it is required to engage the adjusting nut with the piston under a given load to assure that the adjusting nut is kept from turning. This leads to a increase in the number of parts with the resulting rise in cost. In addition, this arrangement is troublesome to assemble.